Anticlockwise evolution of ultrahigh-temperature granulites within continental collision zone in southern India

Carbonic fluid inclusions in ultrahigh-temperature granulite from Kumiloothu in the northern Madurai Block, southern India

“…However, this model is not realistic because of the primary nature of fluid inclusions in garnet, apatite, and rutile which indicates that the fluids were trapped during the prograde to peak metamorphism. Although counterclockwise P -T history as proposed by Santosh and Sajeev (2006) and Tsunogae and Santosh (2006b) from the MGB might be consistent with the occurrence of such low -density carbonic fluid, available textures discussed in this study (e.g., relic staurolite inclusions in garnet) support clockwise history of this locality. An alternate explanation is that, as the rock underwent significant pressure decrease during rapid exhumation along a clockwise trajectory, the fluid inclusions experienced density reversal due to sudden volume changes of the inclusion cavities (e.g., Ohyama et al, 2008).…”

“…An alternate explanation is that, as the rock underwent significant pressure decrease during rapid exhumation along a clockwise trajectory, the fluid inclusions experienced density reversal due to sudden volume changes of the inclusion cavities (e.g., Ohyama et al, 2008). Such near isothermal decompression after the peak event is supported by the occurrence of various corona textures such as orthopyroxene + cordierite and gedrite + sapphirine + spinel symplectites around garnet, and sapphirine + spinel + cordierite symplectite between kyanite and garnet (or gedrite) in this region (e.g., Shimpo et al, 2006;Santosh and Sajeev, 2006;Tsunogae and Santosh, 2007;Tsunogae et al, 2008a;Kanazawa et al, 2008). Such density modification of fluid inclusions has been reported earlier from some of the granulites along the PCSZ Tsunogae et al, 2008b).…”

Electron microprobe dating of monazites from an ultrahigh-temperature granulite in Southern India: Implications for the timing of Gondwana assembly

“…This block as well as the PalghatCauvery Shear Zone system (PCSZ) at its northern margin have been the focus of several recent studies. Sapphirineand corundum -bearing Mg -Al granulites in this region have provided robust evidence for ultrahigh temperature (UHT) metamorphism at extreme thermal conditions of up to 1100 o C and 12 kbar followed by either simple clock -wise or anticlockwise paths, or a multistage exhumation history (e.g., Raith et al, 1997;Sajeev et al, 2004;Tamashiro et al, 2004;Tateishi et al, 2004;Tsunogae and Santosh, 2006;Santosh and Sajeev, 2006). Recent studies have indicated that the whole of the northern Madurai Granulite Block as well as parts of the Palghat -Cauvery Shear zone system experienced extreme thermal conditions, possibly during a common tectonothermal event (Santosh et al, 2006b).…”

Sodicgedrite in ultrahigh-temperature Mg-Al-rich rocks from the Palghat-Cauvery Shear Zone system, southern India

“…Shimpo et al (2006) and Tsunogae and Santosh (2006) reported near eclogite facies high pressure (HP) metamorphism at P>12 kbar and following UHT peak event of T = 940 990 ºC from the PCSS, which is probably related to Neoproterozoic continent continent collision orogeny from this terrane. Available petrological data from adjacent areas along the PCSS also support such HP and UHT metamorphism (Tsunogae and Santosh, 2003;Koshimoto et al, 2004;Santosh and Sajeev, 2006).…”

“…The aim of this short report is to describe new occurrence and chemistry of extremely Na rich gedrite (~ 3.1 wt% Na 2 O) in Mg Al rich rocks from the northernmost flank of the Pan African Madurai Block along the Palghat Cauvery Shear Zone system (PCSS) in southern India. Such high Na gedrite has not been reported in previous studies from this area (cf., Koshimoto et al, 2004;Shimpo et al, 2006;Santosh and Sajeev, 2006) and from other UHT terranes. Shimpo et al (2006) and Tsunogae and Santosh (2006) reported near eclogite facies high pressure (HP) metamorphism at P>12 kbar and following UHT peak event of T = 940 990 ºC from the PCSS, which is probably related to Neoproterozoic continent continent collision orogeny from this terrane.…”